1. Field of the Invention
The invention relates to a hand-held tool which performs a predetermined operation on a workpiece by driving a tool bit.
2. Description of the Related Art
A known electric hammer provides a user with information for improvement of working efficiency. Japanese Patent Publication No. 60-31635 discloses a technique in which a pressing force detector is provided for detecting a pressing load applied when the user performs a hammering operation while pressing a tool bit in the form of a hammer bit against the workpiece, and it is calculated and indicated whether the pressing force detected by the detector is at the optimum.
In the above-described known art, the load applied to the hammer bit is detected by using the pressing force detector. As for detecting the pressing load of the hammer bit, a known sensor can accurately detect whether the hammer bit is under no-load conditions in which it is not pressed against the workpiece or under loaded conditions in which it is pressed against the workpiece and/or the presence or absence of the pressing load under which the load current largely changes. However, such a sensor is not suitable for detection of the magnitude of load under which the change of the load current of the motor is small due to insufficient pressing or excessive pressing.